1. Field of the Invention
The present invention relates to a solid electrolytic capacitor and a method of manufacturing the same. Particularly, the present invention relates to a solid electrolytic capacitor having narrower distance between an anode and a cathode, and a method of manufacturing the same.
2. Description of Related Art
In recent years, due to the increasing speed of a CPU, even a capacitor used for decoupling has been required to have an electrical characteristic having low impedance in a high-frequency area from several MHz to several GHz for the stabilization of power supply voltage and the reduction in high-frequency noise. In addition, to reduce inductance caused by wiring, the placement of decoupling capacitors directly below or near a CPU has been becoming mainstream technique. Furthermore, even if such capacitors are mounted near a CPU, it also requires reliability against the thermal stress caused by the start and stop of the CPU.
Therefore, a decoupling capacitor is required to have low impedance, miniaturization, low-profile, and high-reliability. Currently, such requirements are satisfied by using a plurality of parallel-connected multilayer ceramic capacitors.
However, since a multilayer ceramic capacitor has small capacitance and thereby a large number of them have to be stacked one another to increase the capacitance, it has to compromise the height restriction. Therefore, tens of multilayer ceramic capacitors have to be mounted near a CPU, and it has increased the manufacturing processes.
Accordingly, the effort for a solid electrolytic capacitor having lower size, lower profile, and lower impedance has been made in order to develop a capacitor having capacitance large enough to replace tens of multilayer ceramic capacitors with the single one and lower impedance. Furthermore, since the clock frequency of a CPU has increased to hundreds MHz to several GHz, it has been desired to reduce an equivalent series resistance (ESR) as well as an equivalent series inductance (ESL) to achieve lower impedance.
Japanese Unexamined Patent Publication No. 2006-190929 discloses a solid electrolytic capacitor in which the electrode-wiring distance between a capacitor component and a terminal has been shortened, thereby shortening the current loop to achieve lower ESL. Further, Japanese Unexamined Patent Publication No. 2002-367862 discloses a chip-type solid electrolytic capacitor in which a conductive adhesive is used at an anode and a cathode to narrow the distance between the anode and cathode, thereby shortening the current loop to achieve lower ESL.
In the solid electrolytic capacitor of Japanese Unexamined Patent Publication No. 2006-190929, a conductive paste is used to connect between the cathode terminal and the cathode portion of the component. However, if the distance between the anode and cathode is too narrow in an attempt to achieve lower ESL, the conventional liquid conductive paste will spread to the anode side. Therefore a certain distance between anode and cathode is necessary in consideration of the oozing. Accordingly, there is a limitation in shortening the current loop in an attempt to achieve lower ESL. Furthermore, a similar oozing will also occur in Japanese Unexamined Patent Publication No. 2002-367862 as the distance between the anode and cathode becomes too narrow. In addition, if a silver paste is used as the conductive adhesive for the anode side to lower the connection resistance, a short will occur due to the silver migration in a moisture-resistance load test or the like. Furthermore, it hinders smooth transfer-molding into tight places such as the periphery of component wires during the exterior molding. In addition, since it has a poor adhesive property, interfaces and spaces were created, and the migration could not be suppressed.